Automated system for transporting payloads

ABSTRACT

An automated warehouse storage system including a multilevel storage array is provided. Each aisle has a set of storage levels and each level has storage locations distributed along the aisle. The guideway network extending through the multilevel storage array is configured for autonomous vehicles to move along the guideway network within the multilevel storage array. The guideway network including an inter-aisle guideway spanning at least two of the multiple aisles and a set of guideway levels extending in an aisle of the multiple aisles and disposed so that each guideway level is at a different one of the storage levels and the vehicles on the guideway level can access the storage locations distributed along the aisle. Each set of guideway levels is connected to the inter-aisle guideway forming a common guideway path so that a vehicle can move between inter-aisle guideway and each guideway level along the common guideway path.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/421,408 filed on Jan. 31, 2017, which is a divisional of U.S. patentapplication Ser. No. 14/860,410, filed on Sep. 21, 2015, now issued asU.S. Pat. No. 9,598,239, which is a continuation of U.S. patentapplication Ser. No. 14/213,187, filed on Mar. 14, 2014, now issued asU.S. Pat. No. 9,139,363, which claims the benefit of U.S. ProvisionalPatent Application No. 61/794,023 filed on Mar. 15, 2013, thedisclosures of which are incorporated herein by reference in theirentirety.

BACKGROUND 1. Field

The exemplary embodiments generally relates to an order fulfillmentsystem for use in supply chains.

2. Brief Description of the Related Developments

An order-fulfillment system for use in supply chains, for example inretail supply chains, may fulfill orders for individual product units,referred to herein as “eaches” (also called “pieces”, “articles”,“items” or, generally, any articles available for purchase in retail asa purchase unit, etc.), which are typically packaged and shipped by themanufacturer in containers known as “cases”. The “each” as used hereinfor convenience purposes, may be considered the most granular unit ofhandling in retail supply chains. Conventional operations to fulfillorders for eaches (usually referred to as “each-picking” or“piece-picking”) are generally labor-intensive because they generallyapply man-to-goods processes that are not highly automated.

The broad field of each-picking within retail supply chains can beviewed as comprising two distinct application domains: (1)store-replenishment applications, in which the orders are placed byretail stores and the picked eaches are delivered to those stores andplaced on shelves to be selected and purchased by customers in thestores, and (2) direct-to-consumer applications, in which the orders areplaced by end users and the picked eaches are delivered directly tothose end users. In both domains, an order consists of a series of“order-lines”, each order-line specifying a particular product (or“stock keeping unit” or simply “SKU”) and a quantity (number of eaches)of that product to be delivered. However, there are several importantdifferences in the operational metrics of applications within these twodomains. Store-replenishment applications typically have many fewerorders than direct-to-consumer applications (as there are many fewerstores than end users), but the average number of order-lines per orderis much higher for store-replenishment orders than for typicaldirect-to-consumer order. Also, the average number of units per orderline is far greater for store-replenishment orders than fordirect-to-consumer orders (because stores are buying units to sell tomany customers whereas consumers are buying for their individual use).And most importantly, the total number of order lines for a given SKU(order-lines per SKU), relative to total order lines to be filled duringa given time period, is much higher in the store-replenishment domainthan in the direct-to-consumer domain. This is because stores typicallycarry very similar assortments and order more SKUs in each order, makingit much more likely that a given SKU will be included in a relativelyhigh percentage of orders, whereas consumers have diverse tastes andpreferences and are ordering fewer SKUs, making it more likely that agiven SKU will be contained in a relatively low percentage of orders.

These last two metrics—units per order-line and order-lines per SKU—arefactors in the design an each-picking system, and the differences inthese metrics between the two domains typically results in verydifferent system designs. It is an object of the disclosed embodiment tobe highly cost-efficient and effective in both domains of each-picking,but to provide design flexibility that allows the configuration to beoptimized for the application based on operational metrics. As a result,in different aspects of the disclosed embodiment, the systemconfiguration may be one optimized for each domain as will be discussedfurther below.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the disclosed embodimentsare explained in the following description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a drawing of a simple P-Tote, which is also suitable as anO-Tote in certain applications of the disclosed embodiment.

FIG. 2a is a drawing of a first aspect of the disclosed embodiment,optimized for store-replenishment applications. (Note that the compassrose is inserted as an internal directional frame of reference, withoutreference to true direction.)

FIG. 2b is a drawing of a second aspect of the disclosed embodiment,optimized for direct-to-consumer applications. (Note that the compassrose is inserted as an internal directional frame of reference, withoutreference to true direction.)

FIG. 3a through FIG. 3g are a sequence of drawings showing the componentstructure of the first aspect of the disclosed embodiment of the TSS.

FIGS. 4, 4 b, and 4 c are a set of drawings showing the ramp and segmentswitches within the TSS.

FIG. 5 is a set of drawings showing various views of the R-Bot.

FIG. 6 is a set of drawings showing the spatial relationships betweenR-Bots, bot-beams, guideway rails, and the transition track section bywhich the R-Bot moves between aisles and guideways.

FIG. 7 shows plan and elevation views of the Picking Workstation.

FIG. 8 is a set of drawings showing the design of the Each-Bot and theoverhead track shapes within which it operates.

FIG. 9 shows plan and side elevation views of the Order LoadingStructure.

FIG. 10 shows plan and elevation views of both configurations of theCircular Vertical Conveyor.

DETAILED DESCRIPTION

Referring to FIGS. 2a-2b , there is shown schematic plan views of anexemplary order fulfillment system 10, and portions thereof for use insupply chains in accordance with the disclosed embodiments.

To achieve a very high or even total level of automation, the disclosedembodiment implements a “goods-to-man” (or “goods-to-robot”) processmodel in which autonomous robotic vehicles bring containers of eaches toworkstations where stationary pickers (either human or robotic) pick therequired number of units of each SKU to fill specific order-lines. Eachtrip that brings one of these product containers to a workstation isreferred to as a “SKU transaction.”

The picked eaches are put into “order containers” for eventual deliveryto customers, either stores or consumers. However, unlike most each-picksystems, in which eaches are put into the order containers immediatelyafter being picked, the pick and put transactions in the disclosedembodiment are decoupled: picked eaches are put into intermediatecarriers, specifically other robotic vehicles, which transport them to,and then put them into, the order containers. The benefits of thisprocess model will be seen more clearly below.

(Note: the word “tote”, which is a term of art commonly used in thefield of materials handling to refer to a container that holds materialsbeing stored or handled, is used hereinafter with reference to bothproduct and order containers.)

Thus, the disclosed embodiment can be characterized as a systemgenerally comprised of eleven elements or subsystems:

Product Totes (hereinafter referred to as “P-Totes”) containing thepicking stock of eaches used to fulfill orders;

Order Totes (hereinafter referred to as “O-Totes”) containing the eachespicked to fulfill orders;

a Tote-Storage Structure (hereinafter referred to as the “TSS”) thatstores both P-Totes and O-Totes;

Robotic vehicles that store and retrieve P-Totes and O-Totes within theTSS, which have random access to all locations within a section of theTSS and are therefore called “Roam-to-Desired Destination Bots”(hereinafter referred to more simply as “R-Bots”);

Picking Workstations where human or robotic pickers remove eaches fromP-Totes;

Each Bots (hereinafter referred to as “E-Bots”), the robotic vehiclesthat receive the picked eaches and transfer them into the targetO-Totes;

an Order-Loading Structure (hereinafter referred to as “OLS”) that holds0-Totes for loading and provides a track network for E-Bots;

Order-handling Bots (hereinafter referred to as “O-Bots”), basically anexpanded version of R-Bots, which move empty O-Totes from theCirculating Vertical Conveyor to the shelves of the OLS, and move filledO-Totes from the shelves of the OLS back to the Circulating VerticalConveyor;

a Circulating Vertical Conveyor (hereinafter referred to as “CVC”) thatmoves both P-Totes and O-Totes vertically between different levels ofboth the OLS and the TSS;

a Bot Lift that moves both R-Bots and Order-Loading Bots vertically intoand out of the system (from/to ground level), and moves R-Bots betweentiers;

a Central Control System (hereinafter referred to as “CCS”), consistingof software, computers, and network equipment, which manages all of theresources within the system (including all of the various robots),orchestrates the entire order-fulfillment process and all relatedprocesses, and provides status and control interfaces to human operatorsof the system.

These elements are described in detail below.

Generally, each of the eleven system elements or subsystems is describedin detail below. Although the aspects of the disclosed embodiment willbe described with reference to the drawings, it should be understoodthat the aspects of the disclosed embodiment can be embodied in manyforms. In addition, any suitable size, shape or type of elements ormaterials could be used.

FIG. 1 shows several views illustrating aspects of a representative ToteT. The exemplary Tote T may serve either as a P-Tote, or O-Tote as willbe described further below. The function of the P-Tote is to hold eachesthat comprise the picking stock in the system available for use infilling customer orders. To simplify the design of the entire system inthe various aspects of the disclosed embodiment, all P-Totes are similarsize, i.e. have similar exterior dimensions. The eaches are loaded intothe P-Totes outside the system by manual or automated means, so P-Totesenter the system already loaded with eaches to replenish the pickingstock.

FIG. 1 is a drawing of a simple P-Tote, may be for example of asix-sided container in the shape of a rectangular solid with an open topand a single interior storage compartment. This configuration of P-Totemay be appropriate for storing eaches of a single SKU, as may inpractice be typical for faster-moving SKUs. However, it is highlydesirable to be able to store more than one SKU in a single P-Tote inorder to maximize storage density, minimize the required number ofP-Totes, and thereby enable the economical stocking of slower-movingSKUs. Towards that end, the interior volume of the P-Tote can bepartitioned into multiple storage compartments either by fixed-wallpartitions or by movable walls to enable each tote's configuration ofstorage compartments to be changed. In alternate aspects, the P-Tote issimply a frame that is a carrier of one or more variably-sized,removable sub-totes that actually hold the eaches and can easily bemoved from one P-Tote frame to another (by automated means) in order toconsolidate storage in as few P-Totes as possible.

Whatever the interior configuration, in the exemplary embodiment of theP-Tote, an exterior feature is the presence of “handles” T2 on each(long) side T4 of the tote. These handles may used by robots within thesystem in the transfer of the totes between the robot and either a rackwithin the TSS or a platform on the CVC, as explained in more detailbelow. In one aspect of the disclosed embodiment, the two handles are atdifferent elevations along the height of the tote so that when totes areplaced into storage in similar orientations, the handles on adjacenttotes can overlap each other in vertical space (i.e. one above theother). This arrangement makes it possible for totes to be spaced moreclosely together without interference between adjacent handles, therebymaximizing storage density. The difference in elevation between the twoadjacent handles may be greater than the height of the telescopingtransfer arms of the R-Bot (see below) so that an arm can be extended inthe space below the topmost handle without interference by the lowerhandle.

Note that the eaches can be loaded into the P-Totes (or sub-totes)loose, in which case the “de-trashing” process of disposing of theoriginal shipping-container materials (e.g., cardboard, shrink wrap,etc.) may be performed immediately. Alternatively, the shippingcontainers could be cut open only enough to expose the contained eachesfor picking and then place into the P-Tote Sub-Container with the eachesstill contained inside. In this case the de-trashing process may beperformed later, either at the Picking Workstations or when theP-Tote/Sub-Container returns for the next reloading/picking cycle.

The function of the O-Tote is to hold eaches that have been picked fromP-Totes to fill customer orders. To simplify the design of the entiresystem in the aspects of the disclosed embodiment, O-Totes have similarexterior dimensions as P-Totes. It may of course be possible to designthe system such that O-Totes are different in size from P-Totes, or evenvariably sized. O-Totes in one aspect of the disclosed embodiment alsohave similar two exterior handles as the P-Totes at different elevationsvertically on the (long) sides for use in transfers by robots within thesystem. The desired interior configuration of the O-Tote depends on theapplication. In typical store-replenishment applications, the O-Totesimply has a single open storage compartment, just like the totedepicted in FIG. 1, and filled O-Totes also serve as the shippingcontainers in which the eaches are delivered by truck to the stores tobe placed on the shelves for selection by customers. In typicaldirect-to-consumer applications, in which orders are filled at acentralized fulfillment center and shipped by truck to customers,similar tote design can be used advantageously with variably-sizedsub-containers, such as cardboard boxes, that are the shippingcontainers in which the eaches are sent to the customers. In a differenttype of direct-to-consumer application, such as in an automated retailstore in which customers come to the facility to pick up filled ordersand take them home themselves, the O-Tote may be divided into multiplecompartments by removable “liner bags”, which also serve assub-containers by which customers carry their eaches home, and which areinserted into the O-Totes by manual or automated means.

Tote-Storage Structure (“TSS”), Storage Array 12 (see FIGS. 2a, 2b )

The TSS may be a large rack system with attached guideways 15 for robotsand human-access structures. It serves two functions: (1) it providesstorage for totes of eaches in the system, both P-Totes containing thepicking stock and filled O-Totes that are waiting to be delivered tocustomers, and (2) it provides a closed operating environment for theR-Bots that store and retrieve these totes and transport them betweenstorage locations, Picking Workstations, and CVC.

The TSS may be generally comprised of five elements:

the storage rack 14, which is a multi-aisle 16, multi-level 18 rackstructure that holds the totes in storage and provides the wheel-supportmeans for R-Bots to access the rack in order to store and retrieve thetotes (see also FIGS. 3a-3g );

ramps 20 that connect sets of levels together within an aisle to formzones so that R-Bots can travel to and from any storage level within azone, the number and configuration of such zones being similar for eachaisle;

interconnect 22 or inter-aisle guideways, including rail networks onwhich R-Bots 40 are able to travel between the aisles of the storagerack, the Picking Workstations 30, and the CVC 60;

human-access structures such as walkways, stairways, and floors thatprovide means for service technicians to get into and work within theTSS when necessary, such as to remove a failed R-Bot or resolve otherproblems; and track-control modules (not shown) that communicate withthe CCS and control the position of switches within the guideway railnetworks and ramp, thereby controlling the travel paths of R-Bots.

Aspects of the disclosed embodiment of the topology of the TSS may varyas desired. The first aspect of the disclosed embodiment may be designedfor store-replenishment applications, which generally have a much higherratio of eaches picked per SKU transaction, and therefore many fewer SKUtransactions (i.e., R-Bot trips) for a given volume of eaches shipped,compared to direct-to-consumer applications. In this embodiment, the TSSis optimized for low cost and high space-efficiency, rather than forR-Bot throughput. The second aspect of the disclosed embodiment may bedesigned for direct-to-consumer applications, which have many more SKUtransactions relative to the number of eaches shipped, and the TSS maytherefore be optimized for R-Bot throughput, even though thisconfiguration is somewhat more costly to build and makes somewhat lessefficient use of space, compared to the first aspect of the disclosedembodiment.

FIG. 2a shows a plan view of the first aspect of the disclosedembodiment, for store-replenishment applications. In this embodiment,the TSS is said to have a “single-ended” configuration because ramps andguideways are located at only one end of the storage rack, and R-Botstravel bi-directionally both on the guideways and within the aisles. Forexample, on a typical round trip starting from a pick location insidethe storage rack, the R-Bot picks the assigned P-Tote off the rack,travels West to and up the ramp and onto the guideway, turns South ontothe guideway, travels to and through the Picking Workstation, returns tothe interconnect guideway traveling North, turns into an aisle and godown the ramp to the target level, drives East down the aisle to theassigned put-away location, and finally puts the P-Tote back onto thestorage rack.

FIG. 2b shows a plan view of a second aspect of the disclosedembodiment, in which the TSS is said to have a “double-ended”configuration because ramps and guideways are located at both ends ofthe storage rack. In this configuration, R-Bots travel in only onedirection, in a circulating pattern, thereby eliminating the contentiondescribed above. For example, in the configuration shown in FIG. 2a ,R-Bots travel in counter-clockwise loops, so there is an entry guidewayon the East side of the storage rack on which travel is only Northbound,an exit guideway on the West side on which travel is only southbound,and two interconnect guideways to the South of the storage rackstructure, one for eastbound travel and other for westbound. Theeastbound guideway interconnects the exit guideway and the PickingWorkstations with the CVC and entry guideway, while the westboundguideway enables R-Bots to circulate between the Picking Workstationsand the CVC without having to go through the storage rack. For example,on a typical round trip starting from a pick location inside the storagerack, the R-Bot picks the assigned P-Tote off the rack, travels West toand up the ramp and onto the exit guideway, turns South onto theguideway, travels to and through the Picking Workstation, then travelson the eastbound interconnect guideway, turns North and travels on theentry guideway until reaching the target aisle, turns West and goes downthe ramp to the target level, drives West along the aisle to theassigned put-away location (assuming that it is reached prior to thenext pick location), and finally puts the onboard P-Tote back onto thestorage rack.

The storage rack may include steel columns that are tied together withcross-bracing to form “frames” that provide vertical support for thestructure, and steel beams are attached to the frames to providehorizontal support for the objects being stored within the rackstructure. Pairs of parallel beams form a rack (see FIG. 3a ) thatsupports the totes front and rear, with the totes oriented lengthwiseperpendicular to the beams (FIG. 3b ). Multiple sets of beam-pairsattached to a common vertical frame create a “bay” containing multiplelevels of storage. Multiple bays are constructed in a linear series,with adjacent bays sharing a common frame, to form “modules”, and themodules are arranged in opposing pairs separated by spaces to create“aisles” (FIG. 3c ). Since R-Bots only need access to one end of a toteto effect a transfer, back-to-back modules on adjacent aisles areabutted together, or even structurally integrated to form a singledouble-bay module.

“C-channel” steel shapes are used in the disclosed embodiment for thehorizontal support beams 24 (see also FIG. 4). However, while the openside of the C-channel on an aisle normally faces into the bay and awayfrom the aisle, in the various aspects of the disclosed embodiment, itfaces towards the aisle. This is so that the wheels of the R-Bots canrun within the inside of the “C” shape even with totes being supportedby the outer top surface of the “C” shape. In other words, the C-channelbeam serves both to support totes in storage and to provide a supportmeans for R-Bots to be able to travel within the aisle. Theseaisle-facing C-channels are therefore referred to herein as “bot-beams”.

As described briefly above, at one or each end of every aisle of the TSSis a set of ramps 20, each of which is selectably connected to thebot-beams of multiple vertically-adjacent storage levels by means of amoveable “segment switch” 26 (see FIG. 3d , 4). Each ramp and itsassociated segment switches enable R-Bots to enter and exit any of theattached bot-beams and thereby access any of those storage levels withinthat aisle.

The set of levels interconnected by a shared ramp forms a “zone” ofvertical space within the aisle, and all aisles have a similarconfiguration of zones in terms of height. Ideally all zones within eachaisle have similar height and similar number of levels, though this isnot a desire. The specific number of levels to interconnect to create azone is an application-specific design parameter that generally dependson the available clear height below the ceiling and the height of eachstorage level. However, there is a desire that the height of each zonemay be such that a human can work comfortably and effectively within thezone as the need may arise, which may generally mean that zone heightsmay be a minimum of about six feet and probably a maximum of about ninefeet assuming that a short stepladder can be used by technicians workingin the aisles. For example, in the reference designs shown in FIG. 2aand FIG. 2b , the ceiling clear-height is about 30 feet; the height ofeach level is about 18″. Each ramp interconnects six levels to createzones that are all about 9-feet high, with three zones stackedvertically in each aisle. Since all of the aisles have identical zoneconfigurations, corresponding zones across all aisles can be consideredto form a “tier” within the storage rack (see FIG. 3e ). Thus, in thereference design illustrated in FIG. 2a and FIG. 2b , there are threetiers of nine aisles each in each system.

FIG. 4 shows one side of a ramp 20 and associated segment switches 26for three storage levels. Each side of the ramp structure consists of ahorizontal entry/exit section of standard bot-beam connected to aninclined section of modified bot-beam 27 (see FIG. 4b ), themodification being the removal of portions of the top surface of theC-channel to permit the insertion of segment switches (shown in detailas FIG. 4c ). In alternate aspects the configuration of switches may bereversed, such as with an upwardly inclined ramp from the commonguideway. Each segment switch is actuated by an actuator to be in eithera raised or lowered position, rotating on a hinge joining the top of thesegment to the level's bot-beam. (In the various aspects of thedisclosed embodiment, the two segment switches on a given level may bein similar position, so they are rotated by a single actuator.) When thesegment switches for a given level are in the raised position (like thetop and bottom switches in FIG. 4), the wheels of an R-Bot that ismoving up or down the inclined bot-beam of the ramp remain within theramp and the R-Bot continues on its up or down path, and the wheels ofan R-Bot running within the bot-beam of that level are blocked fromentering the ramp. Conversely, with the segment switches for a givelevel in the lowered position and making contact with the bottom insidesurface of the inclined bot-beam (like the middle switch in FIG. 4),when the wheels of an R-Bot traveling down the ramp encounter thesegment switches, they roll into and through the segment switches andthen into the attached bot-beams of the level, and the R-Bot enters thatstorage level. If the R-Bot is running in the opposite direction, itswheels roll out the bot-beam of the storage rack, through the segmentswitches, and into the inclined bot-beams of the ramp, and the R-Botbegins climbing the ramp.

The angle of incline of the ramps is a design parameter, of course, thetradeoff factors being loss of storage rack on and near the ramps vs theability of the R-Bots to climb the grade. The steeper the angle, theless space is lost for tote storage but the more difficult it is forR-Bots to climb, and also to descend safely. Each guideway 15 consistsof a floor on which an R-Bot rail network is mounted, and its functionis to enable R-Bots to move freely throughout a tier carrying totesbetween the storage rack 14, Picking workstations 30, and the CVC. Inthe first aspect of the disclosed embodiment, for store-replenishmentapplications, vertical space beneath each guideway is precious becausethe OLS occupies the vertical space between the guideways. For thatreason, the guideway floors may b3 “sandwich panels”, such as thoseformed by adhering sheets of metal on both sides of a sheet plywood(called “plymetal” panels), because this structure offers exceptionalstiffness relative to its thickness. As a result, these panels can spansignificant distances without support beams underneath them and withminimal deflection. In the second aspect of the disclosed embodiment, bycontrast, the OLS stands alone, separate from the TSS, so there is amplevertical space between interconnect guideways to construct the flooringusing less costly methods that have a higher vertical profile, such asstandard plywood supported by steel I-beams.

The rail network preferably provides R-Bots 40 active rail-guidance onthe guideways, using standard railroad components (rails and switches),meaning that the switches determine the path of an R-Bot at everybranch. These switches are controlled by the CCS, which also managesmovement of the R-Bots themselves, so the R-Bots on the guideway simplydrive on the rails wherever the switches take them and whenever the CCStells them. Since railroad technology is well known, description of thedetails of rails and switches is not included herein. The TSS involvesthe bi-directional transition of an R-Bot between an aisle and aguideway, but that is best understood in conjunction with the design ofthe R-Bot, as described below.

It is important to note that rail-guidance of R-Bots is by no meansessential to the practice of this disclosed embodiment—self-guidance byR-Bots running unconstrained on the floor may be used.

The rail-guidance is active, with switches in the rail networkcontrolling travel path of each R-Bot, and hence a “Tow-Bot” (or “T-Bot”not shown) may be provided that can couple to an R-Bot that has failedon a guideway and pull or push it to the Bot Lift so it can be taken outof the system. The use of T-Bots may dramatically reduce the need forhuman intervention to resolve problems that might occur, which may inturn reduce the labor costs associated with operating a system, whilealso increasing system availability and reducing MTTR (Mean Time ToResolution).

Another element of the TSS is the set of access structures 70 thatenable human workers to enter the TSS in order to resolve problems thatmight occur, such as malfunctioning R-Bots (see FIGS. 2a, 2b ). For eachtier, there is a walkway at both ends of the TSS (in various aspects ofthe disclosed embodiment), extending across all of the aisles, installedimmediately below the lowest storage level in the tier. For the firsttier, this walkway is of course the floor of the building, and stairs orelevators allow workers access to the walkways all of the upper tiers.In each zone, there is a walkway running the full length of the aisleand connecting to the walkway at each end, by which workers can enterthe zone and reach any point on any level within the zone in order toresolve a problem. (Again, these walkways for the first tier are thefloor of the building.) Since these walkways are installed below thefirst tier in each level, there is no interference with R-Bots runningon that level. Since the wheels of R-Bots are safely captured within the“C” shape of the bot-beams, workers can walk safely on the cross-aislewalkways in front of the ramps, but as mentioned above, lock-out/tag-outmechanisms prevent workers from turning into an aisle and entering azone until all R-Bots have been cleared and the rail switches on therelevant guideway have been positioned to prevent R-Bots from enteringthe zone. It should also be noted that the stairways that provide accessto the cross-aisle walkways can also be configured to provide humanaccess to the guideways.

The R-Bots 40 (see FIG. 5) are the workhorses of the system, performingthe functions of (a) storing and retrieving P-Totes and O-Totes withinthe TSS, and (b) transporting these totes between the TSS 12, thePicking Workstations 30, and the CVC 60. As mentioned earlier, eachR-Bot generally operates within a single tier, although the Bot Lift 90(see FIG. 2a ) enables them to move to different tiers as required tobalance workloads. Within a tier, every R-Bot has access to any aisle(zone) and any storage level, so it can service every tote-storageposition within the tier. On most trips into the TSS, an R-Bot willreturn at least one Product or O-Tote to storage (called a “put away”),and remove at least one Product or O-Tote from storage (called a “pick”,though referring to a tote-pick rather than an each-pick). In order tominimize the amount of travel and thereby maximizeproductivity/throughput of each R-Bot, a put-away almost occurs onsimilar storage aisle/level as a pick. Stated another way, a given totegoing into storage is almost assigned a storage location on similaraisle/level as the next tote to be picked, so an R-Bot can perform botha put-away and a pick on a single trip into the aisle/level.

FIG. 5 shows views of the R-Bot in one exemplary aspect of the disclosedembodiment. Each R-Bot is comprised of the following subsystems:

-   -   a. a chassis frame to which all of the other components are        mounted;    -   b. at least one tote-transfer mechanism by means of which the        R-Bot can transfer P-Totes and O-Totes between itself and either        a storage rack within the TSS or a moving platform on the CVC;    -   c. a propulsion subsystem, consisting of at least one electric        motor, transmission mechanisms, and drive wheels, which provides        the mechanical force that moves the R-Bot;    -   d. an electrical-power subsystem that acquires, stores, and        distributes electrical power used by the various motors,        actuators, sensors, computer and other electronic components;    -   e. an onboard control subsystem comprising a small computer        integrated with sensors and actuators that enable it to control        all of the functions of the R-Bot, and integrated with a        wireless network interface through which it communicates with        the CCS and with other computers on the system network (e.g.        WCS).

The chassis is a structural frame, typically made of steel and/oraluminum, to which all other parts of the R-Bot are attached directly orindirectly. The art in making such structures is well known and so willnot be described further herein.

As shown in FIG. 5, the various aspects of the disclosed embodiment mayinclude the R-Bot having two (or more or less) tote-transfer mechanisms.Each of the transfer mechanisms has two axes of motion: a pair oftelescoping arms can be extended laterally to either side of the bot byan actuating motor, and a pair of lift mechanisms, one fore and one aft,to which each of the telescoping arms is mounted that can independentlymove the two arms vertically.

The R-Bot uses this mechanism to pick a P-Tote or an O-Tote from astorage location by performing the following steps: (1) extend the twotelescoping transfer arms under each of the two handles of the targettote; (2) lift the two arms so that they engage the handles and lift thetote off the rack by a prescribed clearance; (3) retract the transferarms to bring the tote onboard the bot; (4) drop the arms so that thetote is in “stowed” position (as low within the bot as possible). Theprocedure for transferring a stowed tote to the storage rack simplyreverses the steps above: (1) lift the tote to an elevation slightlyhigher than the bot-beam; (2) extend arms so that the tote is nowpositioned over the rack; (3) drop arms so that tote rests on thestorage rack and the arms are in the clear below the handles; (4)retract transfer arms.

In alternate aspects, the bot may have a single transfer mechanism.Having two or more such mechanisms improves R-Bot throughput andproductivity in each of the various aspects of the disclosed embodimentof the system. In the first aspect of the disclosed embodiment,optimized for store-replenishment applications, the two mechanisms allowan R-Bot to carry two P-Totes to the Picking Workstations on each roundtrip. While this doesn't reduce the time spent performing storage andretrieval tasks within the TSS, the trip overhead spent traveling fromthe storage rack to the Picking Workstations, going through theWorkstations, and returning to the storage rack is now amortized overtwo tote-picks instead just one, thereby improvingthroughput/productivity. In the second aspect of the disclosedembodiment, optimized for direct-to-consumer applications, the R-Botcarries only one P-Tote to a Workstation on each trip, but theproductivity gain derives from the facts that R-Bots enter aisles at oneend and exit at the opposite end and that P-Totes are returned tostorage on similar aisle/level of the next pick. If an R-Bot arrives atthe put-away location prior to arriving at the pick location, it canperform the two transfers with only a single transfer mechanism.However, on half of the trips, on average, the R-Bot will encounter thepick location before the put-away location, and the presence of twotransfer mechanisms enables the R-Bot to execute the pick beforeexecuting the put-away. If the R-Bot had only a single transfermechanism it may have to pass the pick location and make the put-awayfirst in order to empty the transfer mechanism and then return back tothe pick location, thereby traveling the distance between the twolocations three times instead of once.

The R-Bot has a dual-drive propulsion subsystem with two separate setsof drive wheels. Two pairs of non-steerable cylindrical wheels mountedon fixed axles are used for travel within the storage rack and up anddown ramps, with the wheels running within the inside of the “C” shapeof bot-beams and ramp beams. The R-Bot is also equipped with fourhorizontally mounted, spring-loaded guide wheels that press against andrun along a vertical surface of the each bot-beams, for example thevertical wall inside the “C” shape, thereby keeping the fixed wheelscentered within the C-channels.

On guideways, though, the R-Bot runs on two railroad-style “steeringbogeys 42”, one fore and one aft, each of which has four conical wheelswith flanges. The term “steering” here only refers to the fact thatthese wheel assemblies rotate on a vertical axis to allow the vehicle topassively follow the track, or “steer”, through a turn. The activedetermination of route, i.e. which way a given R-Bot goes at a branch,is made by the CCS through manipulation of the switches in the tracknetwork.

One of the wheel sets may be sufficient to propel the R-Bot at any giventime and a non-driving wheel set is suspended in the air where it canrotate freely, it is possible and potentially advantageous from a coststandpoint to use a single propulsion motor to drive both wheel setssimultaneously. In alternate aspects, two separate propulsion motors,one for each wheel set may be used. The two motors may share similardrive electronics.

As noted above, the desire for the R-Bots to climb up the ramps is areliability risk if the climb depends on tire adhesion through the botdrive wheels, especially if the angle of the incline is made relativelysteep in order to conserve floor space. For this reason, it is desiredto use supplemental drive means to propel the R-Bots up the ramps. Thiscan be done in one of two ways. The first is to equip the R-Bot itselfwith such supplement drive means. For example, gear devices can bemounted on the fixed-wheel axles of the R-Bots, which engagecomplementary resistance features built into each ramp. In one aspect ofthe disclosed embodiment, this is accomplished using means very similarto the commonplace bicycle transmission, by mounting a toothed gearmounted on both sides of the driven fixed wheel axle(s) (e.g. of nogreater diameter than that of the wheels at the end of the axles), andattaching a length of chain to the ramp structure alongside the lengthof each inclined ramp beam, in a position where the links of the chainwill mesh with the teeth of the rotating toothed gears as an R-Botbegins to climb the ramp. The resistance of the chain then translatesthe rotational force of the axle into linear force that pulls the R-Botup the incline. In other aspects of the disclosed embodiment, the secondapproach to providing supplemental drive means is to build it into theramp structure itself, in effect to provide an external lift mechanism.For example, a motor-driven chain could be installed within the rampstructure that engages a hook or other resistance feature on the R-Botchassis and pulls the bot up the incline without any reliance on thebot's drive motor. When an R-Bot moves in either direction between anaisle a guideway, it may makes a transition from running on the fixedcylindrical wheels within the bot-beams of the aisle to running on thesteerable conical wheels on the guideway rails, or vice versa. FIG. 6 isa drawing that shows how this transition works in the various aspects ofthe disclosed embodiments. At each aisle entry, there is a specialtransitional section of rails and bot-beams that are aligned with eachother, referred to herein as a “t-section”. Within this section, therails overlap the bot-beams, and the tips of the rails within theoverlap (i.e., farthest from the guideway) arc downward slightly. Thebot-beams of the t-section have the top surfaces cut away, so that theircross-sectional shapes are essentially a “J” rather than a “C”. Therails and bot-beams of the t-section connect, respectively, to the railson the guideway and the horizontal entry/exit bot-beam of the ramp. Itmay also be noted that when the R-Bot is running on the rails on theguideway, the fixed cylindrical wheels of a bot are at a slightly higherelevation than when it is running within the bot-beams connecting to theramp. Referring again to FIG. 6, it can be seen that an R-Bottransitioning from the guideway to the aisle will be running on theconical wheels on the rail when it enters the t-section. Before thosewheels reach the point where the rails arc downward, the cylindricalwheels of the R-Bot will be above the bot-beam J-channel of thet-section within the overlapping section, and when the conical wheelsbegin to descend down that arc, the cylindrical wheels will dropdownward and encounter the J-channel. At that point, the loading on theleading wheels of the R-Bot will transfer from the conical wheels to thecylindrical wheels, and the conical wheels will be suspended in air.(When this happens, the weight of the steering bogey will activate amechanical latching mechanism (not shown) that will keep the bogeypointing straight, i.e. in line with the bot's longitudinal axis, andprevent vibration from causing the bogey to rotate out of thatalignment.) Similar load transfers will then be repeated with thetrailing wheels and the transition of the R-Bot from the guideway to theaisle will be complete. When the R-Bot is transitioning in the oppositedirection, from the aisle to the guideway, it will be running on thecylindrical wheels within the bot-beam of the aisle when it reaches thet-section. The conical wheels will initially be above thedownward-arcing section of rail but will then encounter the rail on thatarc. At that point the load will transfer from the cylindrical wheels tothe conical wheels as they ride up the arcing rails, the cylindricalwheels will be lifted off the bot-beam and the leading end of the R-Botwill ride through the t-section and onto the rail network of theguideway. (The loading on the conical wheels will also release themechanical latching mechanism so the steering bogey will be free torotate when it reaches the turn.) Similar load transfers will then berepeated with the trailing wheels and the transition of the R-Bot fromthe aisle to the guideway will be complete. (It is also worth notingthat the R-Bot is designed such that the cylindrical wheels are higherthan the conical wheels by a sufficient distance that the cylindricalwheels clear the guideway rails without interference when the R-Bot isrunning on those rails.)

In the various aspects of the disclosed embodiment, the R-Bots useelectricity as their energy source through a combination of “electrifiedrail” and stored charge. The bots acquire power through an electrifiedrail (which can be either conductive or inductive) installed alongsidethe rail networks on the guideways, and this power is used both to runon the guideways and also to recharge onboard ultracapacitors (or“ultracaps”), which then power the R-Bots when they are within thestorage rack.

Picking Workstation 30 (see FIGS. 2 a, 2 b, 7)

Eaches actually get picked from P-Totes at a variable number of PickingWorkstations, the number of such Workstations being a function of thevolume of eaches that need to be picked during peak periods. FIG. 7shows an aspect of the disclosed embodiment of a Picking Workstation inthe present disclosed embodiment using a human picker to transfer eachesbetween P-Totes and E-Bots. The Workstation includes:

a “tilt-track” 32 fixture on which R-Bots move into “pick position” sothat the picker can remove eaches from an onboard P-Tote (with the R-Bottilted towards the picker to make it easier for the picker to reach intothe P-Tote);

a chair fixture that supports the human picker in an ergonomicallyadvantageous posture; and

an E-Bot track section 90 on which E-Bots move into “put position” sothat the picker can put eaches into their load-carriers.

The role of the picker is simply to remove eaches from presented P-Totesand place them into E-Bot load-carriers. If eaches are still containedwithin partially-opened shipping cases inside the P-Totes, a secondaryfunction of the picker is to de-trash by removing the remainder of theseshipping cases once they are empty and disposing of it. This can bemanaged simply by equipping the Workstation with trash chutes thatdirect this waste material either into a collection container at groundlevel or a conveyor that carries the material to a container orcompactor located elsewhere in the facility.

The operation of the Workstation is managed by a Workstation ControlComputer (“WCS”), which is a subsystem within the CCS. The WCS interactswith the human picker by means of several additional items of equipment:

a display screen which displays the number of eaches remaining to beremoved from the P-Tote;

a headset by which the operator can receive information from the WCSthrough voice synthesis and input information to the WCS through voicerecognition;

a machine vision subsystem that includes a camera mounted at an elevatedposition with a field of view that includes both the R-Bot pick-positionand the E-Bot in put-position, by which it monitors the movements of theoperator's hands (note: white (or visual contrast) gloves can be worn byoperators to make this task faster and more reliable);

weight-sensors that can measure changes in the weight of both the E-Botand R-Bot in order to verify/validate the transfer of the correctnumbers of eaches specified by the order lines being fulfilled.

When an R-Bot or E-Bot enters a queue at a Workstation, as directed bybot-management software within the CCS, it establishes a communicationslink with the WCS and its movements are then managed by the WCS untilits transfers have been completed. The operation of the workstationgenerally consists of the following actions for example, all effectivelycontrolled by the WCS, starting with an R-Bot loaded with a P-Tote inpick-position and an E-Bot in put-position with a load-carrier presentedfor receiving eaches:

The picker's screen displays the number of eaches remaining to be pickedfrom the P-Tote and the WCS sends a synthesized-voice input to thepicker of that number through the earphones on the picker's headset.

The picker reaches into the P-Tote with one or both hands and removesone or more of the target eaches, voicing input to the WCS indicatingthe number of eaches being transferred, and puts those eaches into theload-carrier on the E-Bot.

By reading the output of the weight sensors detecting the weights of theR-Bot and E-Bot, the WCS measures the weight reduction in the R-Bot andthe weight increase in the E-Bot when a transfer is made. One obviousverification check is to compare two weight changes to ensure they areessentially equal in magnitude (within the measurement accuracy of thesensors). Moreover, by dividing the absolute value of this weight changeby the known unit weight of the target SKU's eaches (read from adatabase), the WCS can determine the number of eaches just transferred(again within the measurement capability of the sensing technology), sothe system is not solely dependent on the voice input of pick quantityby the human picker and can thereby detect an “over-pick”, i.e. theremoval of more eaches than have been ordered. Any discrepancy in theresults of these validations may generate an error message andexception-handling logic on the part of the WCS. Otherwise, the eachesare considered successfully transferred and the WCS subtracts thisnumber of eaches from the number of remaining eaches prior to the pickto yield an updated number of units remaining to be picked.

By tracking the picker's hand movements via the vision subsystem, theWCS can literally “see” the transfer process being performed by thepicker. As soon as the picker's hands have moved away from the P-Toteafter removing the last of the remaining eaches to be picked from thatP-Tote, the WCS commands the R-Bot to move forward slightly and presentthe next onboard P-Tote, if there is one; or if there is no otheronboard P-Tote from which to pick, the WCS simultaneously commands theR-Bot to leave the Workstation (passing control of that R-Bot back tothe CCS bot-management software), and the next R-Bot in the queue tomove forward into pick-position. (An exception to this process occurs ifthe picker is also required to de-trash. In this case, the picker mayexecute a voice input after picking the last each from the partiallyopened shipping case, indicating to the WCS that a de-trashing move isrequired. This input causes the entire process to pause so that thewaste material can be removed from the P-Tote and disposed of by thepicker, and after this de-trashing move, the picker can issue a secondvoice command causing the picking process to resume.)

The WCS uses similar methods to manage the movements of the E-Bots. Whenthe weight sensor shows that eaches have been dropped into an E-Bot'spresented load-carrier and the vision system sees the picker's handsmove away from the E-Bot, the WCS commands the E-Bot to rotate itsload-carrier mechanism and present the next empty load-carrier, if thereis one; or if all the load-carriers on the E-Bot are full, the WCSsimultaneously commands the E-Bot to move out of put-position (passingcontrol of that E-Bot back to the CCS bot-management software) and thenext E-Bot in the queue to move forward into put-position and presentthe first empty load-carrier.

One design feature of the pick/put transfer process described above isthat the picking rate is essentially determined by the picker's handmovements as detected by the machine-vision system, because they areused by the WCS to trigger the actions of the R-Bots and E-Bots. As aresult, the picker is controlling the flow of materials at theWorkstation at a rate comfortable to him/her, without any consciousthought or explicit action—if the picker speeds up his/her rate ofpicking, the bots move faster through the Workstation, and vice versa.That being said, there are a number of element of the Workstation'sdesign whose purpose is to enable maximization of the picker'spick-rate, including for example the following:

The donating P-Tote is in proximity to the receiving E-Bot load-carrier,so the picker is moves the eaches a minimal distance—only a fewinches—in order to effect the transfer, thereby minimizing transactiontimes and operator fatigue.

As mentioned earlier, the tilt-track fixture causes the R-Bot—andtherefore the presented P-Tote—to be rotated slightly towards thepicker, making it considerably easier for the picker to reach into thetote and grasp eaches, which also reduces both transaction times andoperator fatigue.

The elevation of the P-Tote is also above the E-Bot load-carrier, so thetransfer is “downhill”, i.e. gravity-assisted, to further minimizeoperator fatigue.

This is a goods-to-man process model and there is a single fixedlocation for both the pick and the put, thus there is zero travel timefor the picker, who can therefore remain in a stationary position allthe time. This very effectively maximizes throughput. The operator isprovided a chair-like fixture specifically designed to provide desiredsupport to the body and minimize fatigue, such as the “kneelsit” chair(see www.kneelsit.com for suitable example). The realized fatigue andrepetitive stresses, which in turn can degrade throughput and, moreimportantly, can be potentially injurious to the picker. The operator isalso able to rotate the chair so he/she can pick with either hand, andso can switch hands to deal with fatigue and repetitive use, and alsocan use both hands simultaneously to pick heavier objects or multipleeaches in a single pick.

Finally, 1 bot moves may occur simultaneously with the picker's moves,and this overlapping of tasks in time minimizes the time a picker maywait for bot moves. For example, while the picker is reaching hands intoa P-Tote to pick eaches, the receiving E-Bot is rotating load-carriersor moving into put position to replace the previous E-Bot, so by thetime the picker has completed the pick and is ready to put the each(es)into an E-Bot load-carrier, the appropriate load-carrier is ready toreceive it. Conversely, while the picker is executing the move to putone or more picked eaches into the receiving E-Bot load-carrier, thedonating R-Bot can be shifting forward to present the next P-Tote ormoving into pick position to replace the previous R-Bot, so by the timethe picker has completed the put and is ready to make the next pick, theappropriate P-Tote is in position to be picked from.

In the alternate aspects an automated picker may be used with a roboticarm in place of the human picker. This may have a machine-vision systemthat can determine the locations and orientation of target eaches topick within the unstructured visual field of loose eaches within theP-Tote, and (b) an end-of-arm effector that can reliably grasp thesetarget eaches and execute the transfer, notwithstanding the very broadrange of sizes, shapes, packaging materials, crushability, and otherattributes of the eaches across the full assortment of SKUs beinghandled. With a robotic picker, moreover, the Workstation may no longerinclude the user-interface components described above, including displayscreen, headset, and chair, nor may it need the weight sensors in orderto validate the correct pick quantity.

In the various aspects of the disclosed embodiment described herein, theP-Totes are carried through the Workstations onboard an R-Bot, as thisis the simplest, “leanest” process model. However, in some applicationswith a high average number of eaches per SKU transaction—such asstore-replenishment applications R-Bot throughput/productivity could beimproved if the incoming P-Tote were instead transferred by the R-Botsto a conveyor, carried through the Workstations by the conveyor, andthen picked up by other R-Bots for the return to storage. In this way,each R-Bot may simply unload its P-Tote(s) on a conveyor, move toanother location to pick a different P-Tote(s) off the conveyor toeither return to storage or if empty to the CVC for removal from thesystem. If the total time required for the R-Bot to complete both ofthese two transfers is less than the average time required to carry theP-Totes through the Workstation, the average R-Bot round-triptransaction time may be reduced, R-Bot productivity may increase, andfewer R-Bots may be required for a given volume of SKU transactions.E-Bots (see FIG. 9).

E-Bots 100 serve as intermediate carriers of eaches from the pickers tothe O-Totes. In materials-handling systems 17 is desired to minimize thenumber of transfers of handled items. Most prior art each-pick systems,even those that employ a goods-to-man process model, adhere to that ruleby having picked eaches placed directly into the receiving ordercontainer immediately after being removed from the product container.However, this “direct-put” method requires both containers to be insimilar places at similar times in order to effect the transfer, andthis constraint (a) adds software and algorithmic complexity, and (b)significantly limits productivity/throughput because it restricts thenumber of order lines for a given SKU that can be filled on each SKUtransaction. This is especially true in large-scale goods-to-maneach-pick systems.

Maximizing the number of order-lines per SKU transaction (“OL/ST”)minimizes the number of SKU transactions (and therefore R-Bot trips) tofill a given volume of order lines, so OL/ST is a metric in optimizingthe productivity of any order-fulfillment system (especiallystore-replenishment applications). Virtually all direct-put systemstherefore have algorithms for increasing OL/ST by scheduling orders tobe filled concurrently that share order lines for similar SKUs. Whateverthe specifics of any such algorithm, its effectiveness in maximizingOL/ST is ultimately a function of the number of orders that canphysically be in-process (or “active”) at the time of each SKUtransaction. In a direct-put, goods-to-man process, the maximum numberof active orders is a function of workstation design and configuration,limited by the number of order containers that are arrayed at theworkstations for filling. The problem is that increasing the number ofactive orders past a certain relatively low threshold degrades pickerproductivity/throughput for a variety of reasons, so workstationsdesigns inevitably may compromise either picker productivity orautomation efficiency (OL/ST) or both, and in a manual system aconsiderably higher priority is usually placed on picker productivity.

However, this conflict between optimization goals can be completelyeliminated by relaxing the constraint of the direct-put method andallowing an additional transfer of the picked eaches into anintermediate carrier that transports them from the Picking Workstationand puts them into the target O-Tote. In the disclosed embodiment, theE-Bot 100 is that intermediate carrier, and its use provides twooperational and system-design capabilities:

Because every E-Bot can access every O-Tote, every Picking Workstationcan fill any order-line from any active order, so on every SKUtransaction it can fill all order lines for that SKU from all activeorders (limited only by the number of eaches in the specific P-Totepresented for picking).

Because of the decoupling of the pick from the put, the number ofconcurrently-open orders is not a function of workstation design and socan be scaled to an arbitrarily large number totally independently ofthe number, size, or configuration of workstations. This means thatOL/ST can be optimized without any impact whatsoever on pickerproductivity.

As shown in the drawing in FIG. 8 of an aspect of the disclosedembodiment, the E-Bot 100 operates suspended from on an overhead trackstructure. It consists for example of the following general components:

a drive assembly located at the top of the Bot;

a main body attached to the bottom of the drive assembly;

an array of at least one and if desired multiple load-carriers attachedto the main body, each such carrier holding for transport eaches from asingle order line;

at least one drop-down transfer mechanism for depositing eaches intoO-Totes through a gravity-assisted transfer (in one aspect of thedisclosed embodiment, the load-carriers also perform this function);

a power subsystem, including conductive or inductive pick-ups foracquiring power from an external power source, and an internal ultracapfor storing power, and

a control subsystem consisting of an onboard computer and otherelectronic circuit boards, and an array of sensors.

The drive assembly includes a main drive motor that turns a verticaldrive shaft that extends upwards and drives an axle to which two drivewheels are mounted that run within the overhead track structure. Exceptat branches and merges, the cross-sectional shape of the track is an“open” rectangle, i.e. there is a gap in the bottom plane of therectangle, which creates a “slot” in the bottom of the track. The twodrive wheels run on the horizontal surface on each side of the slot,with the drive-shaft housing extending through the slot, and thedrive-assembly housing and attached main body suspended below. (Notethat since the E-Bot runs on two wheels, it will hang in a verticalposition below the track even if the track is sloped at an angle offhorizontal.) In the various aspects of the disclosed embodiment,straight sections of the track are fabricated very simply bycold-rolling sheet metal. More complicated sections of the track, suchas curves, branches, and merges (also shown in FIG. 8) are fabricated ascast parts.

The drive assembly also includes two non-driven guide wheels, one oneach side of the drive shaft, each of which is mounted to the unattachedend of a shaft that is pivotably attached at the other end to thedrive-assembly base such that it can be rotated between a vertical(“UP”) position and an off-vertical or horizontal (“DOWN”) position.When a shaft is UP, the attached guide wheel is pressed against theoutside vertical surface of the track, the point of contact beingin-line with the center-axle of the drive wheel assembly inside thetrack. When the guide-wheel shaft is in the DOWN position, the attachedguide wheel is below the bottom of the track so that it can pass underthe track without interference. With both of the shafts in the UPposition (and under tension), the guide wheels keep the drive wheelsrunning straight in-line within the interior of the track, i.e. theyprevent the drive wheels from veering off-line and either scrapingagainst the interior vertical walls or dropping into the center slot ofthe track. With one shaft in the UP position and the other in the DOWNposition, the guide wheels enable the E-Bot to travel through a branchor merge in the track, as explained more fully below.

A variety of track sections are shown in FIG. 8 that, depending on thedirection of E-Bot travel, allow either a single line of track to branchinto two, or two lines of track to merge into one, thereby providingmaximum flexibility in designing E-Bot travel paths within a system.These branch/merge sections include shapes resembling generally theletters “L”, “Y”, and “T” any similar shapes may be used. As can readilybe seen, an E-Bot cannot pass through one of these sections with both ofthe guide-wheels shafts in the UP position without encountering aninterference with one of the two branching or merging tracks, and so oneof the two shafts may be rotated into the DOWN position prior toreaching the branch/merge section of track. In a merge there is only onechoice of which guide-wheel shaft to drop, i.e. the one that mayotherwise encounter the interference with the other merging track.However, in a branch either of the two guide-wheel shafts can be droppedDOWN, and in effect it is the selection of which guide wheel is droppedto DOWN and which remains UP that determines the track that the E-Botselected at the branch. When a single track branches into two, each ofthe two vertical sidewalls of the single incoming track is shared by oneof the two outgoing tracks, and when an E-Bot enters the branch on thesingle incoming track, it will take the outgoing track that shares thevertical sidewall along which the UP guide wheel is running. The E-Botis therefore able to control its path through a branch, i.e. “steer”itself, simply by dropping the guide wheel on the side not connected tothe desired outgoing track.

Whenever a E-Bot travels through any branch/merge track segment, one ofits drive wheels may pass over the slot of the branching or mergingtrack. The guide wheel that may cross this chasm is on the side with theDOWN guide wheel, and the guide wheel that remains in the UP positionperforms a critical role in preventing that drive wheel from droppinginto the slot in the track. At the point where the drive wheel reachesthe slot and there is no longer a horizontal support surface underneaththe wheel, gravity will try to pull the unsupported wheel into the slot,thereby creating a rotational force on the E-Bot in that direction.However, the UP guide wheel resists this rotational force by pressingagainst the outer wall of the track, and the load originally carried bythe drive wheel in question transfers to the UP guide wheel until thedrive wheel passes over the slot and reengages with the roadway surfaceof branched or merged track. (A slight downward lip on each side of theslot helps to smooth the transition of the guide wheel when it leavesthe first roadway surface and when it returns to the roadway surface onthe other side of the slot.)

According to the drawing in FIG. 8, each of the two load-carriers on anE-Bot receives one or more eaches from the picker at the Workstation,holds them as the E-Bot travels to and positions itself over thedestination O-Tote, then is lowered into the O-Tote, and finallyreleases the picked eaches so they are pulled down into the O-Tote bythe force of gravity. Thus, in this embodiment, each load-carriergenerally carries all of the eaches for a single order line beingfilled, so an E-Bot can fill two order lines on each round trip. As canbe readily understood, however, increasing the number of order-linesthat can be filled on each trip will increase the productivity andthroughput of the E-Bots. In the present design, this may beaccomplished by increasing the number of load-carriers: depending on thesize of the largest each to be handled, there might be three or evenfour, and it may also be possible to create more complex designs toincrease the order-line-per-trip capacity of the E-Bot even further.

In FIG. 8, the load-carriers are mounted on the main body such that theycan be rotated. This rotation is used to position the empty loadcarriers to receive eaches sequentially at the Workstation, and again atthe destination O-Tote to position the appropriate load-carrier abovethe target O-Tote (or sub-tote therein) so it can drop down and releasethe load of eaches. In the drawing in FIG. 8, the load-carrier is shownsimply as a rigid container with a bottom surface that can slide open torelease the contained eaches, but the design of the load-carriers may bevaried based on maximum size of the desired load and the accuracy andprecision desired of the drop/release procedure. Like their larger R-Botcousins, E-Bots are electrically powered through a combination of storedpower via onboard ultracaps and electrified rail (either conductive orinductive), which may be most logically installed in the track at theworkstations so the bots could be charging as they wait in queue and in“put-position” to receive eaches.

Order-Loading Structure (“OLS”) 110 (see FIG. 9)

FIG. 9 shows the Order-Loading Structure 110, which includes a rackstructure for temporary storage of O-Totes, and also the E-Bot tracknetwork. (The stand-alone OLS configuration shown in FIG. 9 correspondsto the second aspect of the disclosed embodiment, optimized fordirect-to-consumer applications and shown in FIG. 2b . The OLSconfiguration for the first aspect of the disclosed embodiment,optimized for store-replenishment applications, shown in FIG. 2a , isfunctionally equivalent, though it differs in certain features as aresult of being integrated within the interconnect deck region of theTSS.)

The rack structure for temporary storage of O-Totes resembles the rackstructure of TSS in many respects. It consists of two parallel pairs ofrack modules, each with multiple storage levels, each pair beingseparated by a space to create two aisles within which operate a fleetof robotic vehicles (“O-Bots”) that handle the totes. As in the TSS,bot-beams on the aisles serve both to support the totes in storage andprovide a running surface for the wheels of the O-Bots. The two parallelaisles have loading levels at similar elevations, and the multipleloading levels are connected between the two modules at both ends byend-turn guideways. These guideways, which are comparable in both formand function to their counterparts in the TSS, allow the O-Bots to comeout of one aisle, turn a half-circle on the guideway rails, and enterthe adjacent aisle. (The CVC is positioned at one end of the OLS, theend farthest from the Picking Workstations, and in-line with one or bothof the aisles.)

Each loading level of the OLS includes both the four pairs of beams (twopairs in each of the two aisles) that support the O-Totes, plus E-Bottrack that enable E-Bots to drive to a position directly over any of theO-Totes on that level. As shown in FIG. 9, the configuration of theE-Bot track on every loading level includes a line of track runningaround the perimeters on both sides of each rack module, and at eachO-Tote position on the loading rack the perimeter line is connected by a“T”-shaped track section to a short spur centered over the O-Tote.Optional cut-through segments advantageously enable E-Bots to minimizethe length of the route that may be travelled on each trip. To put aneach into a given O-Tote, an E-Bot travels around the perimeter trackuntil it reaches the target tote, branches onto the spur above thattote, positions itself and drops the eaches into the tote, and thenmerges back onto the perimeter line and either proceeds to anothertarget tote or, if empty, returns to one of the Picking Workstations tobe reloaded.

The E-Bot track network may include means by which E-Bots can movevertically to any of the various elevations at which the multipleloading levels and multiple workstations are located. In one aspect ofthe disclosed embodiment shown in FIG. 9, this elevation-changing meansis a pair of track structures shaped as helixes, one by which E-Bots cango up and the other down. These helixes are positioned between theloading rack and the Workstations, enabling E-Bots to enter and exit thehelixes from either side as they move back and forth between the rackstructure and the Workstations. Since an E-Bot climbing the UP helixwill consume much more power than when running anywhere else within theE-Bot track network, it will likely be advantageous to embed theelectrified rail within this track structure in order to reduce theamount of power that may otherwise have to be stored within theultracaps of the entire fleet of E-Bots. Each helix also has an openingat ground level by which E-Bots can enter into the system (via the UPhelix) or exit the system (via the DOWN helix).

At the Workstations, there is a single line of track servicing each pairof Workstations, where E-Bots queue up for both pickers, and a“Y”-shaped branch at the end of this line where the bots go to onepicker or the other. As mentioned earlier, electrified rail may beinstalled in all of the track at the Workstations, so E-Bots will beable to recharge their ultracaps during this portion of each trip.

The free-standing configuration OLS configuration can be scaled inlength largely independently of the TSS, and so can be made arbitrarilylarge subject to other constraints (e.g. facility limitations).

O-Bots 50 (See FIG. 5)

O-Bots 50 perform the function of moving O-Totes in and out of the OLS,i.e. they receive empty O-Totes being inducted into the system via theCVC 90, place them on the rack to be filled, take them off the rack whenfilled, and put them back on the CVC to be either discharged from thesystem or moved into storage within the TSS by R-Bots. There is at leastone O-Bot per loading level of the OLS, and this number can be increasedas needed to handle the number of O-Totes being moved in and out ofstorage. O-Bots simply travel substantially continuously around the ovalformed by the two storage aisles and end-turn guideways, stopping onlyto transfer O-Totes onto and off of both the storage racks and the CVCplatforms.

The O-Bot is simply an elongated version of an R-Bot (see FIG. 5), withthe extra length used for additional transfer mechanisms to increase thebot's productivity/throughput. For example, while an R-Bot willtypically be equipped with two transfer mechanisms, the O-Bot mighttypically have four.

Circulating Vertical Conveyor (“CVC”) 90 (See FIG. 10)

The CVC 90 moves P-Totes and O-Totes vertically as desired to supportthe order-fulfillment process performed by the system. This includes forexample the following general kinds of moves:

moving filled P-Totes from an inbound conveyor to R-Bots to be placedinto storage within the TSS, thereby replenish the picking stock ofeaches;

moving empty O-Totes from an inbound conveyor to O-Bots to be placedinto the OLS and filled with picked eaches;

moving empty (depleted) P-Totes from R-Bots to an outbound conveyor tobe discharged from the system, typically to be refilled with freshpicking stock and then returned back into storage for another cycle ofdepletion;

moving filled O-Totes from R-Bots and O-Bots to an outbound conveyor fordelivery to customers;

moving filled O-Totes from O-Bots to R-Bots to be placed into temporarystorage within the TSS, pending eventual discharge for delivery tocustomers;

moving filled O-Totes from R-Bots to O-Bots for additional filling, forexample as a result of customers adding items to their orders; and

moving P-Totes between R-Bots on different tiers, to be either pickedfrom or returned to storage, e.g. in order to balance workloads that mayotherwise be imbalanced, for example as a result of non-uniform staffingof Picking Workstations.

Shown in FIG. 10, the CVC 90 is a paternoster lift, a suitable exampleof which are those manufactured by NERAK Systems (seewww.nerak-systems.com/circulating-conveyor.htm). It consists for exampleof a number of load-carrying platforms attached to a pair of closedbelts or chains that are rotated continuously in a rectangle-shapedloop, forming two “columns” of platforms moving in opposite directionsvertically. The platforms are loaded and unloaded while moving, i.e.without stopping. Platforms are loaded while moving upward and unloadedwhile moving downward, and the loading/unloading can take place at anypoint on the vertical path in either direction.

Two configurations of the CVC 90A, 90B are shown in FIG. 10. Both carrymultiple loads (totes) per platform cycle, but the first is“single-sided” 90A in which each platform has only one row of loadpositions (four in the drawing), while the second configuration is“double-sided” 90B in which each platform has two rows of loadpositions. (In this configuration, load positions that face towards theoutside of the CVC at any given moment of time are “outer platforms” andthose that face towards the inside are “inner platforms”.) Thedouble-sided configuration 90B enables transfers in both directions(outbound and inbound) from a single location in the center of the CVC.This capability results from the fact that the outer load positions onplatforms moving in one direction become the inner load positions whenthe platforms transitions to moving in the opposite direction, and viceversa. Thus, an R-Bot or O-Bot in the center of the CVC can offloadoutbound totes onto the inner load positions of rising platforms, whichcan then be unloaded from outside the CVC when the platforms aredescending. Then, from similar locations in the center of the CVC, thebot can on-load totes from the inner load positions of descendingplatforms, which had been loaded from outside the CVC (onto the outerload positions) when the platforms were moving up. Because the bot doesnot have to make a move between the two transfers, as with thesingle-sided CVC configuration, this advantage of bi-directionaltransfer from the center of the CVC also results in somewhat higher botproductivity by comparison.

The first aspect of the disclosed embodiment shown in FIG. 2a uses thesingle-sided configuration of the CVC, 90A with platforms rotating in aclockwise direction when facing North, i.e. platforms on the left sideof the drawing are ascending and those on the right side are descending.The R-Bot and O-Bot travel may be clockwise (if looking down), i.e.Northward on the left-most rail or aisle and South on the rightmost railor aisle. Bots thus enter the offloading transfer location going North,transfer their outgoing totes onto an ascending CVC platform, travelaround the 180° turn, enter the on-loading transfer location goingSouth, and unload totes from a descending platform. The single-sided CVCis most cost-efficient for store-replenishment applications because thevolume of O-Totes is relatively small for a given volume of eachespicked, so the benefit of higher throughput of the double-sided CVC doesnot justify the higher cost.

The second aspect of the disclosed embodiment, optimized fordirect-to-consumer applications and shown in FIG. 2b , uses thedouble-sided CVC 90B configuration, primarily because of its throughputadvantage given the much higher volume of O-Totes relative to the volumeof eaches picked. O-Bots execute all of their transfers from the centerof the CVC, while R-Bots use both center and outside transfer locations.

In both aspects of the CVC, stationary transfer mechanisms interface toinput and output conveyors in order to bring totes into and take totesout of the system. (In the double-sided configuration, these fixedconveyor transfers load and unload the outside-facing load positions;only bots load and unload the center-facing positions.) These transfermechanism can simply be stationary versions of the transfer mechanismson the R-Bots and O-Bots.

It should be noted that in both aspects of the disclosed embodiments,R-Bots and O-Bots load and unload CVC platforms directly. The bots holdthe totes by means of the side handles, while the CVC platforms supportthe totes from the bottom, so the transfers are effected when the botsextend their transfer arms into the path of the moving CVCplatforms—either holding a tote to be transferred to an empty ascendingplatform, or empty to receive a tote from a loaded descending platform.While this is the “leanest” process model, with the minimum number oftransfers and transfer mechanisms, there may be significant benefitsassociated with using intermediate transfers—i.e. the bots may transferto and from fixed transfer mechanisms that may then load and unload theCVC. The four most important of these benefits may include (a) improvingproductivity and throughput of the bots since they mayn't have to waitfor target platforms, (b) improving the reliability of these transfersby eliminating use of the side-handles and having all totes handled fromthe bottom during loading & unloading of the CVC, (c) improving storageefficiency within the TSS somewhat by reducing the width of tote handles(or eliminating them altogether), and (d) reducing the cost andimproving the reliability of R-Bots and O-Bots by eliminating the designdesire that their transfer mechanisms may withstand the moment loadsgenerated when they receive totes moving down on CVC platforms.

Bot Lift 120 (see FIGS. 2a, 2b )

The Bot Lift 120 is a reciprocating lift adapted to carry both R-Botsand O-Bots, primarily through the installation of a pair of bot-beamswithin its load-carrying cab. Bots enter/exit the lift from/to aguideway in similar ways they enter/exit aisles, and ride up and down onthe lift with the four cylindrical wheels captured within the C-channelsof the bot-beams.

Central Control System (“CCS”) 130 (See FIGS. 2a, 2b )

The CCS 130 subsystem manages the overall operation of the system. Itconsists of application software running on one or more “server”computers and communicating via wired and wireless network interfaceswith all of the other active subsystems (R-Bots, E-Bots, TSSswitch-controllers, Workstations, O-Bots, CVC controller, Bot Lift,etc.). Though complex to develop, the application software runs onstandard operating systems and uses standard software platforms,languages, database engines, network communications protocols,development tools, etc., all well known in the art. The following areamong the tasks performed by the CCS and its programming for example:

Managing the induction of O-Totes to replenish the available pickingstock within the TSS, which includes determining the storage locationfor these totes (which will be based at least partially on anoptimization goal of balancing the overall demand for SKU transactionsacross tiers, i.e. so that all the tiers will over time will haveroughly equal numbers of SKU transactions).

Selecting orders to be filled, which can be based on scheduled shippingtimes and various optimization goals, such as maximizing the OL/STperformance metric.

Based on the order-lines to be filled among the selected orders,scheduling SKU transactions.

Assigning R-Bots to bring the specified P-Totes out of storage and carrythem to/through the Picking Workstations, and then to return them tostorage or, if empty to load them onto the CVC. As explained above, eachP-Tote returned to storage will be assigned a new storage location onsimilar storage aisle/levels where the R-Bot's next pick is stored.

Controlling the movement of all the R-Bots within the system, includingcontrolling the positions of switches within the rail networks on theguideways and the segment switches within the ramps so that the bots areable to reach their destinations while avoiding collisions with otherbots.

Controlling the Operation of the Workstations (Via the WCC Subsystem)

Controlling the movement of E-Bots, including travel to their targetO-Totes, the deposit of the picked eaches into those O-Totes, and theirreturn to the Workstation for a next cycle. This task includes atraffic-control function to prevent collisions of the moving E-Bots.

Controlling the activities of the O-Bot, assigning them the tasks ofpicking filled O-Totes from the storage racks of the OLS, placing empty(or partially filled) O-Tote on the storage racks, loading and unloadingthose totes to/from CVC platforms, and controlling all their movements.If there are multiple O-Bots on the OLS loading levels, this latter taskalso includes a traffic-control function to prevent bot collisions.

Monitoring the operation of the CVC, and managing the assignment ofloads to load positions on the platforms, which then drives the timingof the loading and unloading tasks executed by R-Bots, O-Bots, and fixedtransfers at the input/output conveyor interfaces.

Interfacing with external systems to manage the induction ofreplenishment P-Totes and empty O-Totes, and the discharge from thesystem of filled O-Totes and empty P-Totes.

Managing the movement of filled O-Totes into storage within the TSS andthen out of storage for delivery to the customer.

Handling exceptions—dealing with problems that occur when something goeswrong, such as a hardware failure in any of the subsystems, includingthe safe entry of human technicians into the system as required toresolve such problems.

Providing status and operational information, and a control interface,to human supervisory technicians.

In another aspect of the disclosed embodiment, one additional capabilityof the disclosed embodiment may be implemented in a software process.While the primary purpose of the system is order-fulfillment, the use ofE-Bots and OLS makes possible a simple, highly automated process forhandling returned merchandise, often called “reverse logistics”, whichcan is labor-intensive in many prior-art automated each-pick designs.After going through physical inspection and SKU-identification, returnedeaches that are qualified to be placed back into picking stock areloaded into empty P-Totes, one each per tote or sub-tote. (Totescontaining the returned eaches are referred to as “R-Totes”.) When thesystem is ready to process a set of returned eaches, all of the P-Totesin the TSS that contain SKUs associated with the returned eaches arebrought out of storage, but instead of being taken by an R-Bot to thePicking Workstations as usual, they are unloaded by an O-Bot and placedonto a loading rack in the OLS. Once all of these P-Totes have beenstaged within the OLS, the R-Totes holding the returned eaches areinducted into the system via the CVC, and taken to Picking Workstationsby R-Bots. There, the pickers remove all of the eaches in every R-Tote,putting them singly into E-Bot load-carriers, i.e. one each perload-carrier. The E-Bots then travel to and put the eaches into theirrespective P-Totes in the OLS, thereby completing their return topicking stock.

In accordance with one or more aspects of the disclosed embodiment, anautomated warehouse storage system is provided. The automated warehousestorage system having a multilevel storage array with storagedistributed along multiple aisles, each aisle of which has a set ofstorage levels and each level has storage locations distributed alongthe aisle, a guideway network extending through the multilevel storagearray and configured for autonomous vehicles to move along the guidewaynetwork within the multilevel storage array, the guideway networkincluding an inter-aisle guideway spanning at least two of the multipleaisles and a set of guideway levels extending in an aisle of themultiple aisles and disposed so that each guideway level is at adifferent one of the storage levels and the vehicles on the guidewaylevel can access the storage locations distributed along the aisle, anda ramp guideway communicably connecting each of the set of guidewaylevels to the inter-aisle guideway forming a common guideway pathconnecting the inter-aisle guideway and each guideway level so that avehicle moving between inter-aisle guideway and each guideway levelmoves along the common guideway path.

In accordance with another aspect of the disclosed embodiment, at leastone of the guideway levels is selectably connected to the ramp guideway,and the system comprise a controller configured to effect selectionbetween a connected and disconnected state.

In accordance with another aspect of the disclosed embodiment, thesystem comprises a switch between the at least one of the guidewaylevels and the ramp guideway.

In accordance with another aspect of the disclosed embodiment, a vehiclemoving on each guideway level moves along the aisle to storagelocations.

In accordance with one or more aspects of the disclosed embodiment, anautomated warehouse storage system is provided. The automated warehousestorage system having a first storage array, that is a multilevel array,with storage distributed along multiple aisles, each aisle of which hasa set of storage levels and each level has first storage locationsdistributed along the aisle for first containers (the contents of whichare a common retail item), first autonomous vehicles, each configured totransport a first container, a first guideway network extending throughthe multilevel first storage array and configured for the first vehiclesto move along the first guideway network to the first storage locationswithin the multilevel first storage array, the first guideway networkincluding a common guideway common to more than one of the multipleaisles, and guideway levels arranged so that each aisle of the multipleaisles has a set of guideway levels disposed so that each guideway levelis at a different one of the storage levels and the first vehicles onthe guideway level can access the storage locations distributed alongthe aisle, a second storage array with arrayed second storage locationsfor second containers, second autonomous vehicle, and a second guidewayfor the second vehicles to move along the second guideway to the secondstorage locations in the second storage array, and a picking stationconnected to the common guideway for first vehicles to transport firststorage containers from the first storage locations to the pickingstation, and connected to the second guideway for second vehicles tomove from the picking station to the second storage locations, thepicking station connecting the common guideway to the second guidewayand being configured so that contents of the first containers aretransferred from the first containers to the second vehicles. The secondguideway is configured so that each of the second vehicles, when loadedat the picking station, moves from the picking station along the secondguideway to one of the second storage locations, accesses an interior ofthe second container in the second storage location and transfers thecontents from the second vehicle to the second container.

In accordance with another aspect of the disclosed embodiment, thesecond autonomous vehicles independent of the first vehicle.

In accordance with another aspect of the disclosed embodiment, thepicking station is configured so that each retail unit content from thefirst containers is transferred from the first containers to the secondvehicles in substantially one step.

In accordance with another aspect of the disclosed embodiment, whereinthe first containers are inbound or product containers and the secondcontainers are outbound or order containers.

It should be understood that the foregoing description is onlyillustrative of the aspects of the disclosed embodiment. Variousalternatives and modifications can be devised by those skilled in theart without departing from the aspects of the disclosed embodiment.Accordingly, the aspects of the disclosed embodiment are intended toembrace all such alternatives, modifications and variances that fallwithin the scope of the appended claims. Further, the mere fact thatdifferent features are recited in mutually different dependent orindependent claims does not indicate that a combination of thesefeatures cannot be advantageously used, such a combination remainingwithin the scope of the aspects of the invention.

What is claimed is:
 1. A storage and retrieval system comprisingvertically-arranged tote storage locations, the system comprising: aplurality of totes; autonomous robotic vehicles having a propulsionsubsystem; a workstation configured to receive first and second totesvia the autonomous robotic vehicles to consolidate items from within thefirst and second totes into one of the first and second totes to enableincreased item storage density in the totes stored in the tote storagelocations.
 2. The storage and retrieval system of claim 1, furthercomprising a plurality of sub-totes configured to fit within theplurality of totes, the plurality of sub-totes configured to storedifferent stock keeping units (SKUs) of items.
 3. The storage andretrieval system of claim 2, wherein the items are consolidated into oneof the first and second totes by transferring sub-totes containing theitems into the one of the first and second totes.
 4. The storage andretrieval system of claim 2, wherein the plurality of sub-totescontaining the items are of different sizes.
 5. The storage andretrieval system of claim 1, wherein an autonomous robotic vehicletransfers the one of the first and second totes into which items areconsolidated back to a tote storage location.
 6. A storage and retrievalsystem comprising: autonomous robotic vehicles having a propulsionsubsystem; a tote storage structure comprising vertically-arrangedstorage locations; a workstation accessible by the autonomous roboticvehicles, the workstation comprising, at a first time, a first totecomprising a first set of items and a second tote comprising a secondset of items, and the work station comprising, at a second time afterthe first time, the first set of items having been consolidated with thesecond set of items in the second tote to free the first tote of items.7. The storage and retrieval system of claim 6, wherein the first andsecond totes are retrieved from the tote storage structure at a timeearlier than the first time by one or more autonomous robotic vehicles.8. The storage and retrieval system of claim 7, wherein the second toteis returned to the tote storage structure at a time later than thesecond time by one or more autonomous robotic vehicles.
 9. The storageand retrieval system of claim 6, wherein the first set of items arestored in a sub-tote within the first tote at the first time, thesub-tote with the first set of items having been moved to the secondtote at the second time.
 10. The storage and retrieval system of claim6, wherein the first set of items are moved manually from the first toteto the second tote between the first and second times.
 11. The storageand retrieval system of claim 6, further comprising a robotic pickerconfigured to move the first set of items from the first tote to thesecond tote between the first and second times.
 12. The storage andretrieval system of claim 6, wherein, at the first time, the first andsecond totes are first and second product totes for storing items usedto fulfill product orders.
 13. The storage and retrieval system of claim12, wherein, at the second time, the second tote is a product tote forstoring items used to fulfill product orders.
 14. A storage andretrieval system comprising: a plurality of containers; a plurality ofsub-totes configured to fit within the plurality of containers, theplurality of sub-totes configured to store different stock keeping units(SKUs) of items; autonomous robotic vehicles having a propulsionsubsystem and configured to transport the plurality of containers; acontainer storage structure having storage locations configured to storethe plurality of containers; a workstation accessible by the autonomousrobotic vehicles, the workstation comprising, at a first time, a firstcontainer comprising a first set of one or more sub-totes holding afirst set of one or more items and a second container comprising asecond set of one or more sub-totes holding a second set of one or moreitems, and the work station comprising, at a second time after the firsttime, the first set of one or more sub-totes having been consolidatedwith the second set of one or more sub-totes in the second container tofree the first container of sub-totes.
 15. The storage and retrievalsystem of claim 14, wherein the first set of one or more sub-totescomprise a plurality of sub-totes that are consolidated from the firstcontainer into the second container between the first and second times.16. The storage and retrieval system of claim 15, wherein the pluralityof sub-totes in the first set of sub-totes store a plurality ofdifferent SKUs of items.
 17. The storage and retrieval system of claim15, wherein the plurality of sub-totes in the first set of sub-totes areof different sizes.
 18. The storage and retrieval system of claim 14,wherein the first and second containers are retrieved from the containerstorage structure at a time earlier than the first time by one or moreautonomous robotic vehicles.
 19. The storage and retrieval system ofclaim 18, wherein the second container is returned to the containerstorage structure at a time later than the second time by one or moreautonomous robotic vehicles.
 20. The storage and retrieval system ofclaim 14, wherein the first set of one or more sub-totes are movedmanually from the first container to the second container between thefirst and second times.
 21. The storage and retrieval system of claim14, further comprising a robotic picker configured to move the first setof one or more sub-totes from the first container to the secondcontainer between the first and second times.
 22. The storage andretrieval system of claim 14, wherein, at the first time, the first andsecond containers are first and second product totes for storing itemsused to fulfill product orders.
 23. The storage and retrieval system ofclaim 22, wherein, at the second time, the second container is a producttote for storing items used to fulfill product orders.
 24. A method ofoperating a storage and retrieval system comprising a tote storagestructure for storing totes, a workstation and robotic vehicles fortransporting totes to and from tote storage structure and to and fromthe workstation, the method comprising: (a) retrieving first and secondtotes from the tote storage structure by at least one robotic vehicle,and transporting the first and second totes to the workstation, thefirst tote comprising a first set of items and the second totecomprising a second set of items; (b) consolidating the first and secondsets of items into the second tote to empty the first tote; and (c)returning the second tote to the tote storage structure by a roboticvehicle.
 25. The method of claim 24, said step (b) of consolidating thefirst and second sets of items into the second tote comprising the stepof moving one or more sub-totes containing the first set of items fromthe first tote to the second tote.
 26. The method of claim 25, said stepof moving one or more sub-totes from the first tote to the second totecomprising the step of moving a plurality of sub-totes from the firsttote to the second tote.
 27. The method of claim 26, said step of movinga plurality of sub-totes from the first tote to the second totecomprising the step of moving a plurality of sub-totes having aplurality of different SKUs of items from the first tote to the secondtote.
 28. The method of claim 26, said step of moving a plurality ofsub-totes from the first tote to the second tote comprising the step ofmoving a plurality of sub-totes of different sizes from the first toteto the second tote.
 29. The method of claim 24, said step (b) ofconsolidating the first and second sets of items into the second totecomprising the step of manually moving the first set of items from thefirst tote to the second tote.
 30. The method of claim 24, said step (b)of consolidating the first and second sets of items into the second totecomprising the step of automated movement of the first set of items fromthe first tote to the second tote.